Donglai Xu

A high performance CMOS band-gap reference circuit design

This paper presents a CMOS band-gap reference design, which possesses the characteristics of low noise and high power supply rejection capability. Thus, it is suitable for the applications of a wide range of frequency and power input. In order to reduce thermal noise and to provide the output reference voltage that is resistant to power supply variations, the design incorporates an RC filter into conventional reference structure. Moreover, a fast turn-on circuit is introduced into the design to improve turn-on time of the circuit. The simulation results show that within the frequency range from 100 Hz to 10 MHz, the design has achieved an average power supply rejection ratio (PSRR) of more than 80 dB and an average noise of 8.5 /spl mu/Vrms. With the fast turn-on circuit, the improved band-gap reference circuit can reach its steady state within 100 microseconds.

An improved three-step search block-matching algorithm for low bit-rate video coding applications

An improved three-step search (ITSS) block-matching algorithm for motion estimation is described, specifically aiming towards low bit-rate video-coding applications. The method is based on the real-world image sequences characteristic of centre-biased motion vector distribution, and uses centre-biased checking point patterns and a relatively small number of search locations to perform fast block matching. The computational complexity is reduced by employing an 11/spl times/11 search window rather than the traditional 15/spl times/15 window. Simulation results are presented which show that the ITSS algorithm provides better performance at a faster speed than the well-known three-step search (TSS) algorithm and the previously developed new three-step search (NTSS) algorithm when used for low bit-rate video coding, such as in the video telephone and video conferencing.

A Motion Model Based Video Stabilisation Algorithm

Video sequences often suffer from jerky movements between successive frames. In this paper we present a stabilisation method to extract the information from successive frames and to correct the undesirable effects. In the method, the optical flow is computed and the estimated motion vectors using the Horn-Schunck algorithm are passed to the model-fitting unit that stabilizes and smoothens the video sequence. A synchronization module supervises the whole system. The measures based on the fidelity of the system (PSNR) are given to demonstrate the stabilisation and efficiency of the system.

An integrated new scheme for digital video stabilization

In many digital video applications, video sequences suffer from jerky movements between successive frames. In this paper, an integrated general-purpose stabilization method is proposed, which extracts the information from successive frames and removes the translation and rotation motions that result in undesirable effects. The scheme proposed starts with computation of the optical flow between consecutive video frames and an affine motion model is adopted in conjunction with the optical flow field obtained to estimate objects or cameramotions using the Horn-Schunck algorithm. The estimatedmotion vectors are then used by a modelfitting filter to stabilize and smooth video sequences. Experimental results demonstrate that the proposed scheme is efficient due to its simplicity and provides good visual quality in terms of the global transformation fidelity measured by the peak-signal-noise-ratio.

Hybrid Object-Based Video Compression Scheme Using a Novel Content-Based Automatic Segmentation Algorithm

This paper describes a hybrid object-based video coding scheme that achieves efficient compression by separating moving objects from stationary background and transmitting the shape, motion and residuals for each segmented object. In this scheme, a new content-based object segmentation algorithm is proposed, which does not assume any prior modeling of the objects being segmented. The binarization process, which finds large object regions, is based on a threshold function that calculates block histograms and takes image noise into account. The resultant binary mask is further processed using morphological operations. The motion vectors are estimated inside the change detection mask using block-matching method between two successive frames, and then the dense motion field is estimated using the motion vectors and the Horn-Schunck algorithm.

A Scheme for Object-Based Video Segmenation

This paper presents a new video segmentation scheme, which consists of two stages: initial segmentation and motion estimation. In the initial segmentation, the watershed transformation followed by a region adjacency graph guided region merging process is used to partition the first video frame into spatial homogenous regions. Then the motion of changed region is estimated. Based on the highly efficient quadratic motion model, the motion estimation is undertaken using Gauss-Newton Levenberg-Marquardt method to minimize the least-square error function. Experimental results show the proposed scheme provides high performance in terms of segmentation accuracy and video compression ratio.

An Improved Band-Gap Voltage Reference Circuit Design for Multimedia VLSI Systems Integration Applications

This paper presents an improved band-gap voltage reference circuit design for communication and multimedia systems integration applications. The circuit possesses the characteristics of low-voltage, low-power dissipation and low temperature coefficient and is, thus, suitable for mobile communication and multimedia applications. In order to reduce input voltage and power consumption and to provide the output reference voltage that is resistant to temperature and power supply variations, the design uses a MOS peaking current mirror and an improved cascode current mirror to construct self-biasing circuit. The simulation results show that the design has achieved a minimum power supply of 1.5V. With a 3.3V power supply, the power dissipation is less than 40uw, and within the temperature range from –20°C to 70° C, the reference voltage is between 1.3043 ± 0.0005V.

A Flexible VLSI Parallel Processing System for Block-Matching Motion Estimation in Low Bit-Rate Video Coding Applications

In this paper, we design a flexible VLSI-based parallel processing system for an improved three-step search (ITSS) motion estimation algorithm that is superior to the existing three-step search (TSS) algorithm in all cases and also to the recently proposed new three-step search (NTSS) algorithm if used for low bit-rate video coding, as with the H.261 standard. Based on a VLSI tree processor and an FPGA addressing circuit, the proposed architecture can successfully implement the ITSS algorithm on silicon with the minimum number of gates. Because of the flexibility of the architecture, it can also be extended to implement other three-step search algorithms.

Packetization and cell-loss concealment for MPEG-2 video transport over ATM networks

Early re-synchronization technique is a useful method to develop the error free video data in the cells after a lost cell or a transmission error. In this paper, we propose a method in which the MPEG-2 video data is packetized into cells, and the first macroblock in each cell is always located at a special bit, such as an odd bit. Hence, the early re-synchronization method can be improved to halve the computational complexity, while increasing bit-stream data content by only 13 percent. This is because the decoder will not waste its time to decode the macroblock by starting at an even bit. Furthermore, the probability of mis-decoding the macroblock can also be reduced by 50 percent. We also propose another method to utilize the start code in a cell to help correctly decoding the macroblocks located before it. Basic theoretical analysis is presented in the paper to prove that the proposed method is more effective than the existing one. The result show that the effectiveness of the re-synchronization method can be greatly improved by adopting the proposed packetizing technique.